The Music bibliographic format specification is used for printed, electronic, manuscript, and microform music, as well as musical and nonmusical sound recordings.  Material may be monographic or serial in nature.  The designator code MU is often used in written MARC documentation for this material type.

A record created using the MU specifications is identified when Leader/06 (Type of record) contains code c (Notated music), d (Manuscript notated music), i (Nonmusical sound recording), or j (Musical sound recording).

The Music definition of field 006/01-17 and field 008/18-34 is used when the above condition exists.  See 006 and 008:  Music for codes and character position descriptions.